A prospective cohort study is proposed to assess the effects of rotating shift work on adverse reproductive outcomes in China. The investigators will enroll a total of 1,150 women (700 rotating shift workers and 450 regular day shift workers) who currently work in Chinese textile mills, are married, are between 20 and 34 years of age, and are never smokers, who have obtained permission to have a child, and who will be attempting to become pregnant over the course of the study. Reproductive endpoints will include menstrual disturbance, time to conception, spontaneous abortion, preterm delivery, and low birthweight. After enrollment, interviewers will administer a questionnaire to the women and their husbands to collect baseline information on sociodemographic characteristics, use of medications, health status, reproductive history (especially contraceptive use, abortion and infertility), job activities, occupational exposure to dusty chemicals, radiation, noise, and heat, ergonomic aspects, job-related stress, social-support; physical activities, active and passive smoking, indoor coal combustion, cooking oil fumes, indoor coal use, conditioner, consumption of tea, coffee, and alcohol, and diet. Height and weight will be measured by standard methods. Each woman will keep a diary of menstrual bleeding, premenstrual symptoms, use of medications, any illnesses, sexual intercourse, contraceptive use, active and passive smoking, indoor air pollution, alcohol use, water consumption, amount of vigorous exercise and physical activity, emotional upset, and any unusual events or accidents and job activities. Daily urine samples will be collected for each woman for up to one year or until she gets pregnant. Urinary beta- hCG will be measured to identify subclinical pregnancy. The follow-up study and the nutritional survey will be conducted trimonthly. Once a woman becomes pregnant, she will be followed for pregnancy outcomes. The investigators state that this proposed study has several strengths: 1) it will be conducted in a demographically homogeneous population; 2) the risk factor, rotating shift work, is an objective measurement, and therefore should be relatively free of unexpected measurement error; 3) the prospective study design can eliminate the flaws or potential biases in previous cross-sectional off retrospective studies; 4) time to conception and spontaneous abortion will be evaluated with the improved specific biochemical assays to measure beta- hCG, which can detect pregnancy within a few days of implantation; and 5) the study population possesses unique characteristics for examining the proposed hypothesis, i.e., a stable workforce, a non-smoking group, and optimal cooperation. The investigators further state that as there is no reason to expect that the effects of shift work on reproductive outcomes specified in this proposal differ by ethnic status, they believe that the results will be fully generalizable to the U.S. population.